6.4.1 Atoms and isotopes (Green Topic)

Question 1

Radius of an atom=

Answer 1

1 x 10^-10 m

Question 2

How big is the radius of the nucleus?

Answer 2

Radius of nucleus is less than 1/10000 of the radius of the atom.

Question 3

What does the nucleus contain?

Answer 3

The nucleus contains protons (+) and neutrons (neutral).

Question 4

What does what is inside the nucleus mean?

Answer 4

The nucleus has a positive charge. Due to the protons.

Question 5

What is the nucleus surrounded by?

Answer 5

The nucleus is surrounded by electrons (-) in energy levels.

Question 6

Where are energy levels?

Answer 6

Energy levels are at different distances from the nucleus.

Question 7

What is a key idea about energy levels?

Answer 7

Energy levels which are further from the nucleus are at a higher energy than those which are closer to the nucleus.

Question 8

What happens if the atom absorbed electromagnetic radiation?

Answer 8

If the atom absorbs electromagnetic radiation an electron can move from a lower energy level to a higher energy level.

Question 9

What happens when the atom moves to a higher energy level due to electromagnetic radiation?

Answer 9

The atom can now emit electromagnetic radiation and the electron returns back to the lower energy level.

Question 10

What is the smaller number at the bottom called?

Answer 10

Atomic number

Question 11

What does the atomic number tell us?

Answer 11

The atomic number tells us the number of protons, and electrons.

Question 12

Electrons?

Answer 12

Protons have a positive charge but atoms have no overall charge.

That is because the number of electrons is equal to the number of protons.

That means that the negative charges on the electrons cancel out the positive charges on the protons

Question 13

What is the top number called?

Answer 13

Mass number

Question 14

What does the mass number tell us?

Answer 14

The mass number tells us the number of protons + neutrons.

Question 15

Neutrons?

Answer 15

The mass number tells us the total number of protons and neutrons added together.

To calculate the number of neutrons, subtract the atomic number from the mass number.

Question 16

What are isotopes?

Answer 16

Isotopes are atoms of the same element that have different numbers of neutrons.

Question 17

Ions?

Answer 17

Atoms can lose electrons from their outer energy level.

When an atom loses one electron, the ion now has a +1 charge.

If an atom loses two electrons, the ion now has a +2 charge.

Question 18

Similarites between isotopes?

Answer 18

They both have the same amount of protons and electrons

Question 19

Differences between isotopes?

Answer 19

Different number of neutrons.

Question 20

What did the ancient greeks believe?

Answer 20

Everything us made of atoms.

Atoms are tiny spheres which cannot be divided.

This idea was accepted for hundreds of years.

Question 21

Discovery of electrons?

Answer 21

1897: Scientists discovered that atoms contain tiny negative particles. They called these electrons.

This showed that atoms aee not spheres that cannot be divided. Atoms have an internal structure.

Question 22

What was the plum pudding model?

Answer 22

Scientists suggested the plum-pudding model for the structure of atoms.

An atom is a ball of positive charge with negative electrons embedded in it.

Question 23

What were the results of the alpha scattering experiment?

Answer 23

Most of the alpha particles went straight through the gold foil.

Therefore atoms are mainly empty space.

Some of the alpha particles were deflected (changed direction).

Therefore the centre of an atom must have a positive charge and that repelled the alpha particles.

Because some alpha particles bounced straight back.

The mass of the atom must be concentrated in the centre. We now call the central part of an atom the nucleus.

Question 24

What happened as a result of the alpha scattering experiment?

Answer 24

The plum pudding model was replaced with the nucleur model.

Question 25

What did scientist Niels Bohr propose?

Answer 25

Electrons orbit the nucleus at specific distances,

Bohr’s work agreed with the results of experiments by other scientists.

We now call the “orbits” energy levels or shells.

Question 26

Protons and neutrons?

Answer 26

The positive charge in the nucleus is due to positive particles called protons.

James Chadwick discovered that the nucleus also contains neutrons. These have no charge, they are neutral.